I came (because i was asked)
the underline word is

Adverb clause
Adjective clause
Appositive

onto a large boat, and mark the water level that the boat sinks to. then, take the elephant out and put a bunch of marked weights onto the boat until it reaches the same water level. add up the masses of the weights to get the weight of the elephant.

the words “strangest” and “unusual” suggest that the narrator is about to tell the story of an odd or puzzling group of people.